Specific absorption rate (SAR)
Watts of RF power absorbed per kilogram of tissue — the dosimetric quantity behind phone compliance testing, limited to 1.6 W/kg over 1 g in the U.S. and 2 W/kg over 10 g under ICNIRP.
Last verified 12 August 2026.
Also searched as: SAR, W/kg
- Symbol
- SAR
- SI unit
- W/kg
- Units in use
- W/kg, mW/g, mW/kg
What it measures
Energy absorption in tissue during near-field exposure, measured in a liquid-filled phantom at maximum transmit power. Because the U.S. averages over 1 g and ICNIRP over 10 g, the two published numbers for the same phone are not comparable.
Units
Multiplier to the SI unit (W/kg).
- W/kg (watt per kilogram)
- 1 W/kg = 1 W/kg
- mW/g (milliwatt per gram)
- 1 mW/g = 1 W/kg
- mW/kg (milliwatt per kilogram)
- 1 mW/kg = 0.001 W/kg
Related records
- FCC SAR limit for phones and portable devices
1.6 W/kg averaged over any 1 gram of tissue — the number quoted on U.S. phone SAR sheets — plus 0.08 W/kg whole-body.
Exposure limits
- ICNIRP 2020 local SAR basic restriction (head and torso)
2 W/kg averaged over 10 grams of tissue for the general public — a different averaging mass than the FCC's 1 g, which is why SAR numbers are not directly comparable between regions.
Exposure limits
Sources
- fcc-2-1093 47 CFR § 2.1093 — Radiofrequency radiation exposure evaluation: portable devices — U.S. Government Publishing Office (eCFR). regulation, link checked 2026-08-12.
- icnirp-2020 Guidelines for Limiting Exposure to Electromagnetic Fields (100 kHz to 300 GHz) — International Commission on Non-Ionizing Radiation Protection, 2020. guideline, link checked 2026-08-12.
Same record, other formats